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Abstract:

An electronic device includes an electronic device main body, a USB
connection unit, a VBUS detecting unit, a USB control unit, a battery
contained in the electronic device main body, a battery monitoring unit,
a charging control unit, a switch, and, a system control unit that
controls the switch and the charging control unit. The VBUS detecting
unit detects connection of the USB device. If the USB control unit
determines that D+ and D- terminals of the USB connection unit are not
short-circuited, when a battery voltage obtained from the battery
monitoring unit is a preset threshold value or less, the system control
unit starts charging of the battery.

Claims:

1. An electronic device comprising: an electronic device main body; a USB
connection unit provided to the electronic device main body; a VBUS
detecting unit that determines that a USB device has been connected to
the USB connection unit; a USB control unit that detects whether D+ and
D- terminals of the USB connection unit are short-circuited; a battery
contained in the electronic device main body; a battery monitoring unit
that monitors the state of the battery; a charging control unit that
charges the battery; a switch that controls supply of power from the USB
device connected to the USB connection unit to the charging control unit;
and a system control unit that controls the switch and the charging
control unit, wherein the VBUS detecting unit detects connection of the
USB device; and wherein if the USB control unit determines that the D+
and D- terminals of the USB connection unit are not short-circuited, when
a battery voltage obtained from the battery monitoring unit is a preset
threshold value or less, the system control unit starts charging of the
battery.

2. The electronic device according to claim 1, wherein the VBUS detecting
unit detects the connection of the USB device; and wherein if the USB
control unit determines that the D+ and D- terminals of the USB
connection unit are short-circuited, charging of the battery is started.

3. The electronic device according to claim 1, wherein the VBUS detecting
unit detects the connection of the USB device, and if the USB control
unit determines that the D+ and D- terminals of the USB connection unit
are not short-circuited, when the battery voltage obtained from the
battery monitoring unit is a preset threshold value or larger, supply of
power to the charging control unit is not performed.

Description:

TECHNICAL FIELD

[0001] The present invention relates to an electronic device having a
battery-deterioration preventing function of avoiding unintentional
charging, by a user by providing a determining whether to start a
charging when starting the charging through USB, as a technology related
to control on USB charging.

BACKGROUND ART

[0002] Users who charge electronic devices, each of which has a USB
communication function and using a battery as a main power supply, from a
DC power supply of 5V supplied from a VBUS terminal which is a USB
interface of a PC or the like, by use of a dedicated device for USB
charging or a general-purpose USB communication cable, other than
dedicated chargers, as a charging type, have been increasing. The USB
(Universal Serial Bus) is a standard for a serial interface that is set
by a plurality of companies, and is used for published computer systems
and the like.

[0003] A USB cable according to the USB standard has a power supply line
of +5V, a ground line, and two D+ and D- signal lines. The USB cable
according to the USB standard can supply 500 mA at +5V while transmitting
signals. A type of performing charging using this power supply is called
USB charging. In the USB charging, it also is possible to detect a
short-circuited state of the two D+ and D- signal lines on the basis of
the USB standard, so as to determine that a connected device is a
dedicated device for USB charging.

[0004] Further, Micro-USB connectors were standardized and thus it has
been possible to reduce USB connectors in size and thickness and to mount
the USB connectors in portable devices. Therefore, it is fully predicted
that the USB charging will be a standard charging specification for the
future.

[0005] A technology of Patent Document 1 is one of those examples. The
technology of Patent Document 1 is a technology of simply connecting an
output voltage of a VBUS to a power supply line of a portable phone.
However, actually, a method of performing communication and charging
using a general-purpose communication cable available at relatively low
cost in consideration of convenience is general. In this general method,
even in a case where USB connection is performed only for the purpose of
communication, the VBUS is supplied to a charging circuit. Therefore,
charging unintended by a user starts such that the number of times of
unnecessary charging increases, and cycle deterioration is facilitated.

[0006] In contrast, a technology disclosed in Patent Document 2 is an
example of control on charging according power supply from a USB
interface using a general-purpose USB communication cable. An electronic
device disclosed in Patent Document 2 includes a data communication unit
that transmits and receives signals through a USB interface, a
battery-charging control circuit that charges a battery, a distributor
circuit that distributes power of the VBUS for data communication and
charging, a micro computer that concentratedly controls those circuits,
and the like.

[0007] When the data communication unit operates, the distributor circuit
supplies the VBUS power supply to the data communication unit, and when
the data communication unit does not operate, the distributor circuit
supplies the VBUS power supply to the battery-charging control unit,
whereby the electronic device disclosed in Patent Document 2 performs
switching between communication and charging. However, the electronic
device disclosed in Patent Document 2 controls supply of the power supply
to the charging control circuit only on the basis of existence or
non-existence of communication. Therefore, distribution of the
distributor circuit is frequently controlled, that is, start and stop of
charging are frequently repeated. For this reason, in the electronic
device disclosed in Patent Document 2, it is impossible to stop
facilitating deterioration of a charging cycle.

[0008] Patent Document 3 discloses a charging-start control technology
that reduces the number of times of charging, thereby extending the lift
of a secondary battery. The technology disclosed in Patent Document 3 is
implemented by providing a voltage detecting unit that detects the
voltage of the secondary battery, and a switch unit that performs control
such that, when the voltage of the secondary battery detected by the
voltage detecting unit is a predetermined charging start voltage or less,
a voltage is supplied from a charging device to the secondary battery,
and when the voltage of the secondary battery is larger than the
predetermined charging start voltage, the voltage is not supplied from
the charging device to the secondary battery.

[0009] However, in the technology disclosed in Patent Document 3, since
the charging start threshold value is uniformly fixed, in a situation in
which it is predicted that a time interval to the next charging will
lengthen, or the like, at least charging is performed for a long time.
Therefore, even in a case where it is desired to lengthen an available
time, if the voltage of the battery is the threshold value or larger, a
phenomenon in which charging does not start occurs, and thus, convenience
is very bad. In other words, if the threshold value is set to be high,
the number of times of charging increases, and if the threshold value is
set to be low, the convenience becomes bad. Therefore, there is a problem
in which it is impossible to determine a unique threshold value.

CITATION LIST

Patent Document

[0010][Patent Document 1] JP-A-2000-201204

[0011][Patent Document 2] JP-A-2001-202163

[0012][Patent Document 3] JP-A-2002-075463

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

[0013] An object of the present invention is to provide an electronic
device capable of solving the above-mentioned problems, preventing a
cycle deterioration of a battery, and highly-convenient charging control.

Means for Solving the Problems

[0014] In order to solve the above-mentioned problems according to the
related art, as an aspect of the present invention, it is provided an
electronic device which includes a main body, a USB connection unit
provided to the main body, a VBUS detecting unit that determines that a
USB device has been connected to the USB connection unit, a USB control
unit that detects whether D+ and D- terminals of the USB connection unit
are short-circuited, thereby determining whether the connected USB device
is a dedicated device for USB charging, a battery contained in the main
body, a battery monitoring unit that monitors the state of the battery, a
charging control unit that charges the battery, a system control unit
that controls supply of power from the USB device connected to the USB
connection unit to the charging control unit.

[0015] According to the above-mentioned configuration, the electronic
device is characterized in that the electronic device includes a
determining unit that determines whether a connected USB device is a
dedicated device for charging, on the basis of the states of the D+ and
D- terminals of the USB connection unit, when it has been detected that
the USB device has been connected.

[0016] Further, as the aspect of the present invention, the
above-mentioned electronic device is characterized in that, in a case
where it is determined, as a result of the determination on the USB
connection unit that a dedicated charger for USB has been connected,
determination on start of charging based on a charging start threshold
voltage is performed, and in a case where it is determined that a device
other than the dedicated charger for USB has been connected,
determination on start of charging according to the charging start
threshold voltage is not performed.

[0017] As the aspect of the invention, there is provided an electronic
device including: an electronic device main body, a USB connection unit
provided to the electronic device main body, a VBUS detecting unit that
determines that a USB device has been connected to the USB connection
unit, a USB control unit that detects whether D+ and D- terminals of the
USB connection unit are short-circuited, a battery contained in the
electronic device main body, a battery monitoring unit that monitors the
state of the battery, a charging control unit that charges the battery, a
switch that controls supply of power from the USB device connected to the
USB connection unit to the charging control unit, and a system control
unit that controls the switch and the charging control unit, and the VBUS
detecting unit detects connection of the USB device, and if the USB
control unit determines that the D+ and D- terminals of the USB
connection unit are not short-circuited, when a battery voltage obtained
from the battery monitoring unit is a preset threshold value or less, the
system control unit starts charging of the battery.

[0018] Also, as the aspect of the invention, the VBUS detecting unit
detects the connection of the USB device, and if the USB control unit
determines that the D+ and D- terminals of the USB connection unit are
short-circuited, charging of the battery is started.

[0019] Also, as the aspect of the invention, the VBUS detecting unit
detects the connection of the USB device, and if the USB control unit
determines that the D+ and D- terminals of the USB connection unit are
not short-circuited, when the battery voltage obtained from the battery
monitoring unit is a preset threshold value or larger, supply of power to
the charging control unit is not performed.

Effects of the Invention

[0020] As described above, according to the present invention, it is
possible to suppress facilitation of the cycle deterioration of the
battery, thereby extending the life of the battery, while securing
convenience.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a block diagram illustrating a configuration of an
electronic device 1 according to a first embodiment of the present
invention.

[0022]FIG. 2 is a flow chart illustrating an operation of the electronic
device 1 according to the first embodiment of the present invention.

[0023]FIG. 3 is a block diagram illustrating a configuration of an
electronic device 2 according to a second embodiment of the present
invention.

[0024]FIG. 4 is a flow chart illustrating an operation of the electronic
device 2 according to the second embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0025] Embodiments of the present invention will be described below with
reference to the drawings.

First Embodiment

[0026] FIG. 1 is a block diagram illustrating a configuration of an
electronic device 1 according to a first embodiment of the present
invention. Referring to FIG. 1, the electronic device 1 according to the
first embodiment of the present invention includes a USB connection unit
100 provided to a main body of the electronic device, a VBUS detecting
unit 101 that determines that a USB device has been connected to the USB
connection unit 100, a USB control unit 102 that observes the states of
D+ and D- terminals of the USB connection unit 100 and determines whether
the connected USB device is a dedicated device for charging, a secondary
battery 103 contained in the main body of the electronic device, a
battery monitoring unit 104 that monitors the state of the secondary
battery 103, a charging control unit 105 that charges the secondary
battery 103, a switch (SW) 106 that is a switch unit that switches
whether to supply power from the USB device connected to the USB
connection unit 100 to the charging control unit 105, and a system
control unit 107 that controls the switch (SW) 106 and the charging
control unit 105 on the basis of outputs from the USB control unit 102
and the battery monitoring unit 104.

[0027] Next, an operation of the first embodiment of the present invention
will be described in detail with reference to FIG. 2. FIG. 2 is a flow
chart illustrating an operation of the electronic device 1 according to
the first embodiment of the present invention. First, if a user connects
a USB device to the USB connection unit 100 of the electronic device 1,
the VBUS detecting unit 101 of the electronic device 1 detects that the
USB device has been connected, in STEP S200, and notifies the system
control unit 107 that the USB device has been connected, in STEP S201.

[0028] Next, if it is notified by the VBUS detecting unit 101 that the USB
device has been connected, the system control unit 107 turns off the
switch (SW) 106 in STEP S202.

[0029] Also, in STEP S201, it is determined whether a VBUS has detected
that the USB device has been connected to the electronic device 1.

[0030] Next, in STEP S203, the system control unit 107 requests the USB
control unit 102 to perform observation on the states of the D+ and D-
terminals, and the USB control unit 102 notifies the system control unit
107 of the result of the observation on the states of the D+ and D-
terminals. In a case where it is determined as the result of the
observation of the USB control unit 102 on the D+ and D- terminals that
the D+ and D- terminals have been short-circuited, the system control
unit 107 determines that the connected USB device is a dedicated device
for USB charging (`Yes` in STEP S203).

[0031] Then, the system control unit 107 turns on the switch (SW) 106 in
STEP S205, and supplies power to the charging control unit 105, thereby
immediately starting charging the secondary battery 103 in STEP S206.

[0032] Next, in a case where it is determined as the result of the
observation of the USB control unit 102 on the states of the D+ and D-
terminals that the D+ and D- terminals have not been short-circuited, the
system control unit 107 determines that a device other than a dedicated
device for USB charging has been connected using a general-purpose
communication cable or the like (`No` in STEP S203).

[0033] Next, in STEP S204, the system control unit 107 obtains battery
voltage information from the battery monitoring unit 104, and compares a
battery voltage with a preset charging start threshold voltage. In a case
where the battery voltage is the charging start threshold voltage or less
(`Yes` in STEP S204), the system control unit 107 turns on the switch
(SW) 106 in STEP S205, and supplies power to the charging control unit
105, thereby starting charging in STEP S206.

[0034] In a case where the battery voltage is the charging start threshold
voltage or larger (`No` in STEP S204), the system control unit 107 turns
off the switch (SW) 106 such that charging does not start, until the
battery voltage becomes the charging start threshold voltage or less.

[0035] As described above, in the present embodiment, only in a case where
a device other than a dedicated device for USB charging is connected,
determination on whether to start charging is performed on the basis of
the charging start threshold voltage, whereby it is possible to suppress
facilitation of the cycle deterioration of the battery, thereby extending
the life of the battery, while securing convenience.

[0036] Further, although it has been described in the present embodiment
that the determination is performed on the basis of the result of a
single threshold value determination in consideration of processing time,
the present invention is not limited thereto, but the determination may
be performed on the basis of the results of multiple threshold value
determinations.

[0037] Here, in the electronic device 1 according to the first embodiment,
the system control unit 107 compares the battery voltage included in the
battery voltage information obtained from the battery monitoring unit
104, with the preset charging start threshold voltage for the battery
voltage. However, the value of the battery voltage obtained from the
battery monitoring unit 104 is an example of the battery voltage
information. In an electronic device 2 according to a second embodiment,
another example of the battery voltage information will be described.

Second Embodiment

[0038] Next, an operation of the second embodiment of the present
invention will be described in detail with reference to FIGS. 3 and 4.
FIG. 3 is a block diagram illustrating a configuration of an electronic
device 2 according to a second embodiment of the present invention. In a
configuration of the electronic device 2 according to the second
embodiment of the present invention, identical components to those of the
first embodiment are denoted by the same numerals.

[0039] Referring to FIG. 3, the electronic device 2 according to the
second embodiment of the present invention includes a USB connection unit
100 provided to a main body of the electronic device, a VBUS detecting
unit 101 that determines that a USB device has been connected to the USB
connection unit 100, a USB control unit 102 that observes the states of
D+ and D- terminals of the USB connection unit 100 and determines whether
the connected USB device is a dedicated device for charging, a secondary
battery 103 contained in the main body of the electronic device, a
battery monitoring unit 204 that monitors the state of the secondary
battery 103, a charging control unit 105 that charges the secondary
battery 103, a switch (SW) 106 that is a switch unit that switches
whether to supply power from the USB device connected to the USB
connection unit 100 to the charging control unit 105, and a system
control unit 207 that controls the switch (SW) 106 and the charging
control unit 105 on the basis of outputs from the USB control unit 102
and the battery monitoring unit 204.

[0040] Here, the electronic device 2 according to the second embodiment is
different from the electronic device 1 according to the first embodiment
in that the system control unit 207 compares a remaining battery level
included in the battery voltage information obtained from the battery
monitoring unit 204 with a preset charging start threshold voltage for
the remaining battery level.

[0041] Next, an operation of the electronic device 2 according to the
second embodiment of the present invention will be described with
reference to FIG. 4. FIG. 4 is a flow chart illustrating an operation of
the electronic device 2 according to the second embodiment of the present
invention. First, if a user connects a USB device to the USB connection
unit 100 of the electronic device 2, the VBUS detecting unit 101 of the
electronic device 2 detects that the USB device has been connected, in
STEP S300, and notifies the system control unit 207 that the USB device
has been connected, in STEP S301.

[0042] Next, if it is notified by the VBUS detecting unit 101 that the USB
device has been connected, the system control unit 207 turns off the
switch (SW) 106 in STEP S302.

[0043] Also, in STEP S201, it is determined whether a VBUS has detected
that the USB device has been connected to the electronic device 2.

[0044] Next, in STEP S303, the system control unit 207 requests the USB
control unit 102 to perform observation on the states of the D+ and D-
terminals, and the USB control unit 102 notifies the system control unit
207 of the result of the observation on the states of the D+ and D-
terminals. In a case where it is determined as the result of the
observation of the USB control unit 102 on the D+ and D- terminals that
the D+ and D- terminals have been short-circuited, the system control
unit 207 determines that the connected USB device is a dedicated device
for USB charging (`Yes` in STEP S303).

[0045] Then, the system control unit 207 turns on the switch (SW) 106 in
STEP S305, and supplies power to the charging control unit 105, thereby
immediately starting charging the secondary battery 103 in STEP S306.

[0046] Next, in a case where it is determined as the result of the
observation of the USB control unit 102 on the states of the D+ and D-
terminals that the D+ and D- terminals have not been short-circuited, the
system control unit 207 determines that a device other than a dedicated
device for USB charging has been connected using a general-purpose
communication cable or the like (`No` in STEP S303).

[0047] Next, in STEP S304, the system control unit 207 obtains battery
voltage information from the battery monitoring unit 204, and compares a
remaining battery level with the preset charging start threshold voltage.
In a case where the remaining battery level is the charging start
threshold voltage or less, the system control unit 207 turns on the
switch (SW) 106 in STEP S305, and supplies power to the charging control
unit 105, thereby starting charging in STEP S306.

[0048] In a case where the remaining battery level is the charging start
threshold voltage or larger (`No` in STEP S304), the system control unit
207 turns off the switch (SW) 106 such that charging does not start,
until the remaining battery level becomes the charging start threshold
voltage or less.

[0049] As described above, in the present embodiment, only in a case where
a device other than a dedicated device for USB charging is connected,
determination on whether to start charging is performed on the basis of
the charging start threshold voltage, whereby it is possible to suppress
facilitation of the cycle deterioration of the battery, thereby extending
the life of the battery, while securing convenience. Further, although it
has been described in the present embodiment that the determination is
performed on the basis of the result of a single threshold value
determination in consideration of processing time, the present invention
is not limited thereto, but the determination may be performed on the
basis of the results of multiple threshold value determinations.

[0050] Although the present invention has been described in detail with
reference to the specific embodiments, it is apparent to those skilled in
the art that it is possible to apply various alterations and corrections
without departing from the spirit and scope of the present invention.

[0051] This application is based on Japanese Patent Application No.
2010-272194 filed on Dec. 7, 2010, and the contents of Japanese Patent
Application No. 2010-272194 is incorporated here as a reference.

INDUSTRIAL APPLICABILITY

[0052] The electronic devices according to the present invention that have
a function of controlling start of charging according to a result of
detection on a connected USB device have effects of being able to
suppress facilitation of a cycle deterioration of a battery, thereby
extending the life of the battery, while securing the convenience of
charging.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

[0053] 1, 2 ELECTRONIC DEVICE

[0054] 100 USB CONNECTION UNIT

[0055] 101 VBUS DETECTING UNIT

[0056] 102 USB CONTROL UNIT

[0057] 103 SECONDARY BATTERY

[0058] 104, 204 BATTERY MONITORING UNIT

[0059] 105 CHARGING CONTROL UNIT

[0060] 106 SWITCH (SW)

[0061] 107, 207 SYSTEM CONTROL UNIT

Patent applications by Tomoki Katsumata, Kanagawa JP

Patent applications by PANASONIC CORPORATION

Patent applications in class CELL OR BATTERY CHARGER STRUCTURE

Patent applications in all subclasses CELL OR BATTERY CHARGER STRUCTURE